A sharp thermal contrast between the cold forearc and the hot arc and backarc is considered fundamental to various subduction-zone processes. However, direct observational evidence for this contrast is rather limited. If this contrast is present, it must cause a rheological contrast in the mantle wedge: elastic in the forearc and viscoelastic in the arc and backarc for the timescale of earthquake cycles. Here we demonstrate that postseismic deformation following large subduction earthquakes provides independent evidence for the thermally controlled rheological contrast. Specifically, we show that seaward postseismic motion is deflected upward at the edge of the cold forearc mantle wedge, causing diagnostic uplift just seaward of the volcanic arc. From numerical simulations of postseismic deformation following the 2011 moment magnitude (M_w) 9 Tohoku-oki, 2010 M_w 8.8 Maule, 2007 M_w 8.4 Bengkulu and 1960 M_w 9.5 Chile earthquakes, together with a global synthesis of postseismic uplift measurements, we find that cold forearc mantle is present irrespective of the diversity in tectonic settings. Our findings also indicate that field surveys eight years after the 1960 Chile earthquake provided some of the earliest evidence for viscoelastic postseismic deformation. We suggest that the established link between long-term thermal processes and short-term earthquake cycle deformation is important to understanding subduction-zone dynamics.

冷前弧与热弧和弧后之间的强烈热对比被认为是各种俯冲带过程的基础。然而，这种对比的直接观察证据相当有限。如果存在这种对比，它必须在地幔楔中引起流变对比：在地震周期的时间尺度上，前弧是弹性的，弧和弧后是粘弹性的。在这里，我们证明了大俯冲地震后的震后变形为热控制流变对比提供了独立的证据。具体来说，我们表明，向海的震后运动在冷前弧地幔楔的边缘向上偏转，导致火山弧向海的诊断性隆起。来自 2011 年矩震级后的震后变形的数值模拟 (M _w ) 9 Tohoku-oki, 2010 M _w 8.8 Maule, 2007 M _w 8.4 Bengkulu 和 1960 M _w 9.5 智利地震，连同震后隆起测量的全球综合，我们发现无论在构造设置。我们的研究结果还表明，在 1960 年智利地震 8 年后的实地调查为粘弹性震后变形提供了一些最早的证据。我们认为，长期热过程和短期地震周期变形之间已建立的联系对于理解俯冲带动力学非常重要。